Normally, a basic rack (that goes across the front only) like this one comes with at least 2 mounting brackets on the cross bars and 2 on the uprights, for a total of 4 places to mount a cymbal or tom.

A larger rack that wraps around 3 sides usually comes with a couple more tom/cymbal brackets plus the ones on the uprights, but it depends on the manufacturer.

Gibraltar has one that is an in-between size, with a bar that goes across the front, and "wings" that fly off each side for cymbals or toms. That one comes with 4 tom/cymbal mounts and 2 on the uprights, for a total of 6.

No matter what, you can always buy more tom/cymbal brackets, they run like $20-$30 USD. The actual arms that the tom hangs off of usually come with the kit, but they can be ordered separately, too. Pearl, Gibraltar, PDP all make really good rack hardware, it's just a matter of preference. I like the square tubing on the Pearl ICON racks because I've had Gibraltar mounts slip (even ones cranked down super tight). Others swear by Gibraltar, so YMMV.